Characterization of endoglucanase from Paenibacillus sp. M33, a novel isolate from a freshwater swamp forest

The newly isolated Paenibacillus sp. M33 from freshwater swamp forest soil in Thailand demonstrated its potential as a cellulose degrader. One of its endoglucanase genes from Paenibacillus sp., celP, was cloned to study the molecular characteristics of its gene product. The celP gene was recognized firstly by degenerate primer designed from Paenibacillus endoglucanase gene, and subsequently identified flanking region by inverse PCR technique. The celP gene consists of an open reading frame of 1707 bp encoding for 569 amino acids including 33-amino acids signal sequence. CelP is a member of glycoside hydrolase family 5 appended with a family 46 carbohydrate-binding module. CelP from recombinant Escherichia coli was purified by affinity chromatography. SDS-PAGE analysis of purified CelP showed a protein band at about 60 kDa. The purified enzyme gave a specific CMCase activity of 0.03 μmol min^-1  mg^-1 . It had higher activities on lichenan (0.19 μmol min^-1  mg^-1 ) and barley β-glucan (0.14 μmol min^-1  mg^-1 ). Maximum activity on lichenan was obtained at 50 °C, pH 5.0. CelP was stable over a pH range of 3.0-10.0 and retained 80% activity when incubated at 50 °C for 1 h. The properties of its CelP endoglucanase, especially substrate specificity, will make it useful in various biotechnological applications including biomass hydrolysis.